Rolls of toilet paper and paper toweling typically comprise a paper product wound upon a hollow core. The roll is typically supported for rotation on a spindle which extends through the hollow core.
A preferred core shape for dispensing a paper product is a cylinder having a geometrically circular cross-section. A core with a circular cross-section freely rotates about the axis of the spindle and permits smooth, quiet dispensing of the paper product from the roll. However, a core having a hollow circular cross-section has a relatively large void space. It is desirable to reduce such void spaces to improve shipping and storage efficiencies.
One improvement to core wound paper products includes diametric compression of the roll, such that the core has a generally flattened configuration with reduced core void space. The flattened core configuration permits the core wound product to be shipped and stored more economically and in higher densities.
Several attempts have been made in the art to realize the benefits of compressed core wound paper products. Examples of compressed core wound paper products are disclosed in the following references: U.S. Pat. No. 401,233 issued Apr. 9, 1889, to Wheeler, U.S. Pat. No. 972,668 issued Oct. 11, 1910, to Wheeler; U.S. Pat. No. 1,005,787 issued Oct. 10, 1911, to Sibley; U.S. Pat. No. 4,762,061 issued Aug. 9, 1988, to Watanabe, U.S. Pat. No. 4,886,167 issued Dec. 12, 1989, to Dearwester, U.S. Pat. No. 4,909,388 issued Mar. 20, 1990, to Watanabe, U.S. Pat. No. 5,027,582 issued Jul. 2, 1991 to Dearwester; PCT International Publication Number WO 92/11196 Published Jul. 9, 1992, by Dearwester et al.; and G.B. Patent 709,363 issued May 19, 1954, to Samson.
While the compressed rolls taught in these references reduce hollow core void space, they suffer from one or more drawbacks. First, conventional cores can be unstable in the flattened configuration. This instability is characterized by the flattened core buckling and taking on a crescent shaped configuration when the forces compressing the roll are removed and rerounding forces are applied. This tendency to take on a crescent shaped configuration is also known as core inversion, and results in a closed core cross-section rather than an open cross-section. An inverted core having a closed cross section requires considerable effort on the part of the consumer to open the core cross section so that the core can be inserted onto a spindle.
Second, previously compressed cores can have unstable configurations when rerounded. A compressed core will generally have folding creases, vertices or other lines of weakening which cause such instability when the core is rerounded. Once the core is rerounded, radially inward directed forces on the roll can cause the core to reflatten along these same weakened lines. Reflattening of the core results in an undesirable non-circular core cross-section. A non-circular core cross-section results in wobble and noise as the roll is rotated on the spindle to dispense the paper product.
Third, previously compressed cores, when rerounded, often have a non-circular cross-section. Flattening of the core for compression creates flat core sections connected at folding creases or vertices. The rerounded core will have a polygonal cross-section having a relatively flat side corresponding to each folding crease or vertex. A rerounded core having a non-circular cross-section is undesirable for the reasons listed above.
Accordingly, it is an object of the present invention to provide a core which has a generally flattened configuration which resists core inversion upon rerounding. It is a further object of the present invention to provide a core having a rerounded configuration that resists reflattening. Yet a further object of the present invention is to provide a core having a rerounded, generally circular cross-section.